10 m2 within 3m of every door + rainwater collection

You know how all buildings currently require a certain number of parking spaces, due to building laws? How about this:

Food Justice = Land and Water access = 10 square meters of at least 5-hour solar access within 3 meters of the door of every residence and workplace per resident or worker and Rainwater collection from every roof.

Implicit in this vision is that everyone should garden.

The urban landscape would look very different.

Currently our society cares about parking (everyone should have a place to park her car at home and at work and everywhere else).

A society that cares about food justice would have different building codes.

10 sq m is approximately 100 sq feet. Following John Jeavons, each person probably needs at least 30 m2 to grow enough food for themselves and the soil (it may be more, but I have to check).

So there's still a place for farmers in this vision as people won't be growing all their food.

"Within three meters of the door" comes from the permaculture concept of the intensive annual-based garden needing to be in Zone 1, which consists of the places we easily visit, due to routine, every day.

Some communities--such as some places in Australia and Earthaven Ecovillage already implement policies like this.

I believe Christopher Alexander has designed some high-density developments in Japan around principles like these (every household needs a garden). The Nature of Order, III:316-330 {Thanks, Joel, for the reference.}